With further development of thinner, smaller, and lighter portable equipment, a thinner semiconductor chip to be incorporated into the equipment is demanded.
The thickness of the current wafer used for the semiconductor chip is 125 μm through 150 μm, and the development of a thinner wafer of 25 μm through 50 μm has been realized.
The thinner wafer as above is produced by a grinding/polishing process for thinning the thickness of the wafer, a process of performing reverse side processing, etc., and is finally divided into a plurality of semiconductor chips.
When a wafer becomes thinner, the wafer cannot maintain its form by itself, and is easily bent or falls into difficulty in handling.
Therefore, the wafer is normally adhered to a hard supporting plate (hereinafter referred to as a support plate), and the wafer is handled with each support plate in each process.
Among the methods for thinning a wafer using the above-mentioned support plate, there is a method which includes a process of forming a film on the reverse side of the wafer after a grinding/polishing process.
In this case, a document discloses a method of embodying a thinner wafer by using a protection tape not to have an influence of contamination caused in the grinding/polishing process when the film is formed.
When the protection tape is used, the protection tape is adhered in advance on the reverse side of the support substrate (corresponding to the support plate) to which the semiconductor wafer is adhered, and the reverse side of the semiconductor wafer is ground/polished with the protection tape adhered.
Then, after the grinding/polishing process, the contaminants attached to the wafer and the support substrate are cleaned off, the protection tape is stripped off, and a film forming process is performed so that only a small number of contaminants are attached to the support substrate (for example, refer to patent document 1).
The support plate used when a wafer is thinned has been variously newly developed having, for example, through holes, a flat surface without holes, etc.
Among them, a support plate having the through holes is used when a wafer is adhered to the surface of the support plate by a material capable of moderating the adhering power later (for example, there is an adhesive etc. whose adhering power is moderated by alcohol, and the material group like this is referred to adhesive member hereafter.).
The through holes are formed as paths for a dissolving solution (detaching solution) for detaching the wafer once adhered from the support plate, and arranged in a range of an openings in which the wafer is adhered to the support plate.
In each of the processes during producing a semiconductor, the wafer is handled by a working robot holding the support plate, and fixed to a predetermined position by the vacuum adsorption, electrostatic adsorption, etc. on the reverse side of the support plate.
However, when the support plate of this type is used, there has been the problem that dimples occur at the positions corresponding to the through holes on the surface of the wafer after detached from the support plate.
FIG. 6 is a perspective view of the wafer on which the dimples occur. As shown in FIG. 6, a number of dimples 90 occur on a surface 9-1 of a wafer 9.
The dimples 90 can be caused by, for example, a grinding/polishing device fixes a support plate not shown in the attached drawings but adhered to the surface 9-1 onto the table with the wafer 9 facing upward by vacuum adsorption to grind/polish the wafer 9 into a thinner plate by pushing down a grinding wheel etc. onto an exposed surface (reverse side of the wafer) 9-2 of the wafer 9 from above the wafer 9 as follows.
First, the adhesive member not shown in the attached drawings but interposed between the wafer 9 and the support plate by the pressing force of a grinding wheel etc. is depressed at the opening of the support plate. Second, the adhesive member is taken into the opening of the support plate through the through holes by the vacuum adsorption of the reverse side of the support plate, thereby generating the dimples.
Patent Document 1: Japanese Published Patent Application No. 2005-150434